WTT Control Systems & SCADA 2 — Questions and Answers
Question 1: In a wind turbine SCADA system, what does the term 'polling interval' refer to?
- The time between scheduled maintenance checks
- The frequency at which the SCADA system queries RTUs or PLCs for data (Correct answer)
- The interval at which wind speed is averaged for power curve calculations
- The delay between a fault occurring and an alarm being triggered
Correct answer: The frequency at which the SCADA system queries RTUs or PLCs for data
Polling interval is the frequency at which the SCADA master station requests updated data from remote terminal units (RTUs) or PLCs.
Question 2: Which communication protocol is most commonly used for serial communication between SCADA systems and older wind turbine controllers?
- DNP3
- Modbus RTU (Correct answer)
- IEC 61850
- PROFINET
Correct answer: Modbus RTU
Modbus RTU is the most widely used serial communication protocol for legacy SCADA-to-controller communication in wind turbines due to its simplicity and broad device support.
Question 3: A wind turbine's yaw control system uses a 'yaw error' signal. What does this signal represent?
- The angular difference between the nacelle heading and the wind direction (Correct answer)
- The torque load on the yaw drive gearbox
- The number of yaw drive motor starts per hour
- The accumulated yaw cable twist angle
Correct answer: The angular difference between the nacelle heading and the wind direction
Yaw error is the angular difference between the nacelle's current heading and the measured wind direction, used to command the yaw drive to realign the rotor with the wind.
Question 4: What is the purpose of a 'deadband' setting in a wind turbine PID controller?
- To prevent the controller from responding to small, insignificant error signals (Correct answer)
- To limit the maximum output power of the generator
- To define the range of wind speeds for partial-load operation
- To set the minimum rotor RPM before grid connection
Correct answer: To prevent the controller from responding to small, insignificant error signals
A deadband prevents the controller from making unnecessary corrections when the error signal is within an acceptable range, reducing actuator wear.
Question 5: Which sensor is primarily used to provide feedback for closed-loop pitch control in modern wind turbines?
- Strain gauge on the tower base
- Accelerometer mounted on the nacelle
- Encoder or resolver on the pitch bearing or motor (Correct answer)
- Proximity sensor on the rotor hub
Correct answer: Encoder or resolver on the pitch bearing or motor
An encoder or resolver mounted on the pitch motor or bearing provides precise blade angle position feedback to the pitch controller for closed-loop control.
Question 6: In SCADA alarm management, what is a 'nuisance alarm'?
- An alarm that triggers repeatedly without an actual fault condition (Correct answer)
- An alarm that requires immediate shutdown of the turbine
- An alarm generated by a faulty SCADA server
- An alarm that cannot be acknowledged by the operator
Correct answer: An alarm that triggers repeatedly without an actual fault condition
A nuisance alarm is one that activates frequently without representing a true fault, often due to improper setpoints or sensor noise, leading to operator desensitization.
Question 7: What does 'availability factor' measure in wind turbine SCADA performance reporting?
- The percentage of time a turbine is capable of producing power when wind conditions permit (Correct answer)
- The ratio of actual energy output to theoretical maximum energy output
- The percentage of time wind speed exceeds rated wind speed
- The number of hours per year the turbine operates at full rated power
Correct answer: The percentage of time a turbine is capable of producing power when wind conditions permit
Availability factor is the percentage of time a turbine is operational and able to generate power (excluding downtime for faults or maintenance) relative to total elapsed time.
WTT Control Systems & SCADA 2
In a wind turbine SCADA system, what does the term 'polling interval' refer to?